1. To add the ‘Add to Cart’ button simply add the trigger text [wp_cart:PRODUCT-NAME:price:PRODUCT-PRICE:end] to a post or page next to the product. Replace PRODUCT-NAME and PRODUCT-PRICE with the actual name and price. For example: [wp_cart:Test Product:price:15.00:end]
2. To add the shopping cart to a post or page (eg. checkout page) simply add the shortcode [show_wp_shopping_cart] to a post or page or use the sidebar widget to add the shopping cart to the sidebar.